GA-NIFS: An extended [O III] λ5007 halo around the sub-Eddington quasar J1342+0928 at z = 7.54

The James Webb Space Telescope (JWST) opened a new observational window on the primordial Universe. Here we present new JWST NIRSpec integral field spectroscopy (IFS) observations of the z = 7.54 quasar ULAS J1342+0928 obtained as part of the Galaxy Assembly with NIRSpec IFS (GA-NIFS) GTO programme. The new data-set obtained with both the prism (R similar to 100) and the high-resolution grating (R similar to 2700) allow for a complete description of the quasar emission from the rest-frame UV to optical bands. The low-resolution data reveal the presence of [O III] emission on similar to 7 kpc scales, well above the typical galaxy size at this redshift, likely associated with a past outflow event. Additionally, the high-resolution observations show a more energetic ionised outflow on nuclear scales (less than or similar to 0.8 kpc). The total ionised mass outflow rate ranges between similar to 100 and 2200 M-circle dot yr(-1), with a mean (median) value of 480 (390) M-circle dot yr(-1), where the significant spread is mostly due to the lack of tight constraints on the electron density and outflow geometry. This range broadly encompasses the star formation rate range (85-545 M-circle dot yr(-1) ), yet this only represents a lower limit to the total mass outflow rate. By employing an accretion disc modelling, for the first time on JWST data, we manage to robustly estimate the black hole mass and the bolometric luminosity, log(M-BH/(M-circle dot)) = 9.1 +/- 0.2 and log(L-bol/(erg s(-1))) = 46.8 +/- 0.1, respectively. We derive an Eddington ratio of lambda(Edd) similar to 0.4, challenging the paradigm of widespread super-Eddington accretion in quasars at the epoch of re-ionisation. Lastly, we measure the most distant broad line ratios (Fe IIUV/Mg II and Fe IIopt/H beta) so far. Interpreting these ratios as proxies to the broad line region metallicity, we find evidence for an early metal enrichment in quasars within 700 Myr from the Big Bang.